08 eng seed prod guide april1

8/6/2019 08 ENG Seed Prod Guide April1

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Seed Production Guide

Prepared by B.R. Ntare


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Contents

Technical Aspects of Groundnut Seed Production .............................................. 1

1. Introduction ....................................................................................................... 1

2. Site selection .................................................................................................... 1

2.1 Soil selection .........................................................................................................1

2.2 Climatic conditions ...............................................................................................1

2.3 Field isolation ........................................................................................................2

2.4 Rotation .................................................................................................................2

2.5 Soil preparation .....................................................................................................2

2.6 Sowing ...................................................................................................................3

2.7 Fertilization ............................................................................................................4

2.8 Crop maintenance ................................................................................................4

2.9 Irrigation .................................................................................................................5

2.10 Phytosanitary protection ........................................................................................5

2.11 Harvesting/Digging ...............................................................................................9

Post-harvest technology....................................................................................... 11

1. Introduction..................................................................................................... 112. Handling of the harvested crop ..................................................................... 11

2.1 Curing .................................................................................................................. 11

2.2 Stripping/Winnowing .......................................................................................... 12

3. Seed processing ............................................................................................. 13

3.1 Sieving ................................................................................................................ 13

3.2 Density separator ............................................................................................... 13

3.3 Packaging ........................................................................................................... 14

4. Seed storage and conservation .................................................................... 14

4.1 On-farm storage of pods .................................................................................... 14

4.2 Collective or industrial storage .......................................................................... 15

4.3 Storage of shelled groundnuts .......................................................................... 15

4.4 Some technical aspects of the industrial preparation of ready-to-usegroundnut seeds ................................................................................................ 16

5. Phytosanitary protection of stored seeds ..................................................... 19

5.1 Insect control ...................................................................................................... 20

6. Seed physiology ............................................................................................. 22

6.1 Germination ........................................................................................................ 226.2 Dormancy and methods for breaking dormancy ............................................... 23


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Technical Aspects of Groundnut Seed

Production

1. Introduction

One of the most efficient means for the African farmer to improve the productivity

of his farm is by the use of high quality groundnut seeds. Organizing high quality

seed production and distribution is critical to the implementation of any

development plan. This precondition also applies to other factors that affect

productivity. Pod and grain size of a specific variety is an important parameter

for determining seed value. The crop should be grown under appropriate

conditions of climate and soil fertility to ensure good pod formation, filling, and

seed maturity. Cultivation techniques must be perfectly mastered in order for

the plant to attain its full potential and ensure quality production. These standards

are fundamental for producers who want to sign up for a national multiplication

program. The farmer must also accept controls and conform to production

certification standards.

2. Site selection

Under low rainfall conditions, seeds should be produced in the most suitable

areas in order to maximize potential production. This also minimizes transport

and marketing costs.

2.1 Soil selection

Groundnuts prefer light soils that facilitate penetration of the gynophores (pegs)

after pollination, and easy digging without pod loss. Groundnuts required well

drained sandy loams and must not be sown in shallow soils exposed to erosion.

Groundnut plants are sensitive to salinity, a little sensitive to alkaline soils but

they prefer soil with a neutral pH. High soil acidity (pH


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as drought resistant with performances that make it one of the main crops

cultivated in dry tropical areas. However, good performance is strongly linked

to adequate soil water content at sowing time, followed by well-distributed

rainfall. The life cycle of the groundnut can be divided into four phases thatcorrespond to variable water requirements. For a 90-day variety grown under

conditions in the Sahel, the requirements are as follows:

vegetative growth (0-20d): 3.5 mm/d;

flowering (21-40d): 5.2 mm/d;

pod formation and filling (41-70d): 4.4 mm/d;

maturation (71-90d): 3.9 mm/d.

Early small-seeded groundnut varieties require 300-500 mm of rainfall and late

large seeded-varieties 1000-1200 mm.

2.3 Field isolation

Groundnuts are self-pollinating and therefore do not require isolation. Different

varieties must be placed 5-10 m apart to avoid mixing during harvesting and

stripping.

2.4 Rotation

Groundnut is very sensitive to the preceding crop and must not be cultivated for

several consecutive years. A well-adapted rotation program could improve the

efficiency of fertilizer use, soil structure, weed and volunteer plant control, and

reduce pest pressure. Nematodes and certain foliar diseases transmitted by soil-

borne pathogens can be partially controlled with an appropriate rotation program.

2.5 Soil preparation

In semiarid regions, removal of crop residues that spread diseases and harbor

pests is a priority activity. For light soils, this type of cleaning followed by a

shallow raking is often done after the first light rains. This eliminates early weeds

and breaks up the soil surface where seeds are sown soon after the first substantial

rainfall. In wetter areas or with heavier soils, fields must be ploughed at the

beginning of the cycle to suppress weeds and break up the soil, which must then

be refined by harrowing. With this soil type, raised-beds are often made to limit

run-off or plant asphyxia by standing water. The beds can be wide and flattened

at the top in order to accommodate two rows per bed.


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1 Insecticide2 Fongicide

2.6 Sowing

Before sowing, seeds must be carefully prepared. The preparation depends on

the way they were stored. When stored in shell, groundnuts must be preferably

hand-shelled and sorted in order to eliminate skinned, immature, moldy, andsmall seeds. Seeds are then treated with an insecticide/fungicide mixture to protect

them against insects and fungi during germination. The most common are:

carbofuran1 , heptachlor1, captafol2 , thiram2, benomyl2, captan2, carbendazim2,

etc., depending on the regulations of the country where they are used.

Planting date is linked to rainfall distribution in the area and the length of the

variety growth cycle. Soil moisture must be sufficient to guarantee good

germination. Seeds must not be sown immediately after heavy rains since theyimbibe too much water, which causes rotting. This also results in excessive soil

compaction, which may hinder germination.

Spacing depends on the growth habit and the variety: 10 to 20 cm between

plants, and 40 to 60 cm between rows. Planting density is also affected by water

availability, and cultivation methods (flat or raised beds, manual or mechanized).

In addition, the spacing must allow plants to cover the soil within 50 days ensuring

better weed control and rational water use. In rain-fed crops, density varies

between 110 000 (Virginia) and 170 000 (Spanish) plants per hectare. This canbe as high as 250 000 plants/ha under irrigated conditions. The weight of seeds

in shell required to sow one hectare is called the seeding rate (SR). This depends

on varietal characteristics, seed quality and planting density. The SR is calculated

as follows:

Density (plants/ha) weight of 100 seeds (g)

10 seed viability (%) shelling yield (%)

With manual sowing, individual seeds are sown 3-5cm deep. Mechanized sowingis widely practiced in Senegal. This is done using a single row planter, generally

drawn by a horse or donkey. In this way, one hectare can be sown in 8 hours. A

disk adapted to the seed size, turns inside of a hopper and regularly dispenses

the seeds into a furrow opened by the planter blade. A weighted rear wheel then

closes the furrow.

SR =


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2.7 Fertilization

A reasonable level of organic matter must be maintained in the light, weakly

structured, tropical soils where groundnuts are grown. The groundnut plant has

an extensive root system that allows it to explore a large volume of soil andtherefore benefit from organic manure residues from preceding crop (cereal).

Groundnuts can be cultivated with an N-P-K type mineral fertilizer. Calcium

must be added to slightly acidic soils to correct the pH and improve the technical

quality of the seeds. Calcium deficiency leads to a high percentage of aborted

seeds (empty pods or pops) and improperly filled pods. Calcium is barely

translocated across the leaves, therefore it must be applied near the fruiting

zone (as a side dressing). This must be done at the beginning of pod formation

in order to be directly absorbed by the pegs and the young developing pods.The quantity of fertilizer needed to maintain a seed-producing field depends on

soil type and varies between 200 to 600 kg/ha of gypsum for large-seeded

varieties.

2.8 Crop maintenance

2.8.1 Hoeing Weeding

Early hoeing affects future crop growth since it allows better infiltration of

rainwater, controls early weeds and therefore prevents competition for water, a

scarce resource in the Sahel. Hoeing facilitates careful removal of volunteer

groundnut plants from previous crops and incorporation of chemical fertilizers

applied after sowing. Hoeing can either be manual or mechanical. The first hoeing

is generally followed by one or two manual weedings. The crop must completely

cover the soil from the 50 to 60 days, thereby limiting weed growth. Chemical

weed control is uncommon, however, application of a pre-emergence herbicide

would result in possible savings in time and labor, which could be better be

spent on other work. This technique also requires specialized equipment as wellas knowledge of chemical products and their application methods.

2.8.2 Culling out off-type plants

This consists of manual removal of plants of other varieties present in the field.

Depending on the degree of contamination, a field can be retained or rejected

for seed production. In Senegal, fields of mother seeds should have less than

one off-type in 1000 and those of certified seeds, one in 200. Applied standards

for varietal purity of groundnut seeds are as follows; a minimum purity of 98%for level 1 seeds, and 95% for level 2 seeds. Regular field checks allow elimination


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of foreign plants based on phenotypic characteristics of the cultivated variety.

Purifying the field maintains the genetic quality and can only be effective if

checks are rigorously continued throughout downstream operations (removal

of foreign pods during shelling, cleaning of equipment, warehouses and packagingmaterial).

2.9 Irrigation

Although groundnut is a rustic plant, high yield seed production can be guaranteed

using irrigation, especially for first generations. Irrigation also allows off-season

(outside of the rainy season) groundnut production, which accelerates seed

multiplication in Sahelian countries. Quality production is ensured using an

irrigation program adapted to crop demand at each developmental stage.Different irrigation methods can be used including overhead (sprinkler, etc.),

drip and furrow irrigation. The latter is the most commonly used in West Africa

but does not always ensure homogenous water distribution, especially in large

fields. Telethermometry is a useful tool for managing irrigation systems. It links

water demand to the temperature of the canopy and facilitates optimum water

supply, and thereby avoids wastage of water resources. Individual or communal

irrigated fields must be privileged partners for seed production since input usage

(fertilizer, lime, phytosanitary protection) recommended for seed production is

rewarded by high yield and quality.

2.10 Phytosanitary protection

Groundnuts are exposed to pest and disease attack that can cause deterioration

of the quality of the product and lead to significant losses. Some of the most

common diseases are as follows:

2.10.1 Foliar diseases

Groundnut rosette is a disease caused by a virus complex (combination of

several viruses) transmitted by an aphid, Aphis craccivora Koch. There are

three forms of the disease: chlorotic, mosaic or green. The green form occurs

mainly in West Africa. Infected plants are stunted and production is greatly

reduced. The disease can be controlled using resistant varieties along with specific

cultural practices (early, high density sowing). Chemical control is often difficult

and not economically feasible.

Peanut Clump Virus (PCV) is a soil and seed borne disease. Continuous culturefavors its development. Infected plants are stunted and have symptoms such as


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mottling, mosaic, and chlorotic rings on the leaves. They must be removed and

contaminated fields must be excluded from any seed multiplication program.

Peanut Mottle Virus (PMV) is a viral disease. Symptoms include dark greenirregular patches on young leaves. These are not easily seen on older leaves but

a fine mottling can be observed with backlighting.

Early and late leaf spot are diseases caused by fungi that commonly occur in

groundnuts. Early leaf spot, Cercospora arachidicola, causes dark brown

necrotic lesions surrounded by a chlorotic halo on the upper leaf surface. Late

leaf spot, Phaeoisariopis personata, causes almost circular necrotic lesions that

are very dark brown. Spores are produced on the leaf under surface. At high

disease incidence, chlorotic infected foliage prematurely senesces and falls.Although chemical control is effective, it is not very profitable since several

treatments are required during the vegetative growth phase of the crop. Farmers

also have to try to control groundnut rust at the same time.

Groundnut rust (Puccinia arachids) is a widespread fungal disease. Orange

pustules appear on the lower leaf surface and necrotic lesions can occur on any

aerial plant part. Unlike leaf spots, rust causes necrotic leaves to dry out but

remain attached to the plant. Crop rotation is recommended in order to limit

infestation, like for leaf spots.

Other foliar diseases can also be observed. These include Sclerothium leaf spot,

andAlternaria wilts.

2.10.2 Soil borne diseases

Aspergillus niger, Aspergillus flavus, Macrophomia phaseolina and

Rhyzoctonia solani are the most common pathogens causing seed rot during

sprouting. Sorting and treating seeds before sowing are the most effective and

economically feasible means of controlling these diseases. IfMacrophomia is

identified as the causal agent, infected groundnut plants must be uprooted and

destroyed.

2.10.3 Soil pests

The most extensive field damaged is caused by millipedes, termites, white grubs

and nematodes.


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Millipedes (Myriapoda) attack young seedlings and developing pods. They cause

significant damage and are difficult to control. Seedling damage can be limited

by incorporating an insecticide into the seed treatment.

Termites (Isoptera)Macrotermes sp.,Microtermes sp. and Odontotermes sp.

are widespread throughout Africa. They can cause extensive damage in the

field, especially under conditions of water stress when they attack plant by

excavating through the central axis of main roots and stems. They equally attack

developing pods, this can be recognized by holes made under the beak of the

pods. Crop damage is most severe just after harvesting. Termites cause extensive

scarring of the pods which makes them brittle. The pods are then perforated and

the seeds eaten. This creates a gateway forAspergillus flavus. Treating seeds

before they are sown controls termites during the first month. However, forproduction of first level seeds, an insecticide like carbofuran (a carbamate) is

recommended at a dosage of 10 kg per hectare around 40 days after planting.

The residual activity of this insecticide ensures control up until the harvest. This

broad-spectrum insecticide also partially controls millipedes and has some effects

on nematodes. At harvest, soil must be dusted with insecticide before groundnuts

are stacked for curing.

White grubs (Coleoptera) Schizonycha spp. are the larvae of small brown

chafers. They are found in the pod development area and feed on roots, nodules

and pods. Damage symptoms include yellowing and rapid wilting of the plant.

These larva attack several plant species, however, groundnut infestation is

fortuitous. Constant monitoring and chemical control must be included in any

on-farm IPM (Integrated Pest Management) strategy.

Nematodes (Scutellonema cavenessi) are found through out the Sahel. The

nematode is a soil dwelling round worm, less than 1 mm long, which bores into

roots and pods. Nematode presence in the roots severely decreases the numberof nodules and the activity of the nitrogen-fixing bacteria. Infected plants have

yellowish foliage and severely reduced production. Pod damage is first

characterized by the appearance of small brown spots. These become larger and

darker as the nematodes grow. This type of damage can be partially controlled

using a systemic insecticide such as carbofuran. Large scale trials conducted in

Senegal showed that average pod yield can be increased by 500 kg/ha using

dibromochloropropane (DBCP) soil treatments after the first rains, which

stimulates nematode activity.


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2.10.4 Foliar insect pests

These can be divided into two groups: piercing-sucking insects and defoliators

(chewing insects), most of which belong to the orders of coleoptera or

lepidoptera.

The groundnut aphid (Homoptera: Aphidiae), Aphis craccivora Koch, is

commonly called the black groundnut aphid. The black adult is 2-3mm long.

Reproduction is always parthenogenic and there are several generations per

year in tropical climates. Development from nymph to adult takes 5-6 days.

These piercing-sucking insects feed on nutrients produced by the plant and

damage can be particularly severe during prolonged periods of drought. Aphids

form numerous colonies on leaf undersurfaces and on young shoots. They canequally be detected by the fungi (sooty moulds) that develop on the honeydew

excreted by aphids. This species is the vector of groundnut rosette virus. Chemical

control with 300 g a.i./ha of dimethoate has been reported to be very effective.

Thrips (Thysanoptera) are small, slender insects, 2 mm long and 0.5 mm wide.

They can be either yellow, brown or black. The wings are fringed and the tarsi

have a vesicle called an arolium that allows them to stick to slippery surfaces.

The most common thrips that attack groundnut in Africa are Scirtothrips dorsalis,

Thrips palmi, Frankliniella schultzei andHeliothrips indicus . Thrips are piercing-sucking insects. They destroy the parenchyma of the plant with their short stylets

and so reduce photosynthetic capacity. Reproduction is often parthenogenic

and they can produce up to 15 generations per year, especially under hot humid

climatic conditions. Apart from the use of resistant varieties, chemical treatment

with 15 g a.i./ha of Deltamethrine (Decis) or with systemic products can be

used to control high infestations.

Leafhoppers (Heteroptera) are tiny insects belonging to the family Cicadellidae-

Jassidae. Several species of the polyphagous genus Empoasca ( E. kerri, E.

fasciallisandE. lybica) are among the most important insect pests of groundnuts

in Senegal. These insects can cause direct damage by removing plant nutrients

from the parenchyma and by injecting toxic enzymes that cause organ

malformation. Egg oviposition into the tissues can also cause wounds with

secondary effects. Most of these species are vectors of viruses or mycoplasmas.

Drought stress increases damage. The main symptoms include leaf rolling near

leaf bases, yellowing of leaflet tips, stunting, shortening and malformation of

the internodes (dwarfism). Chemical treatment with systemic products likedimethoate (200-250g a.i./ha) provides effective control.


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Caterpillars (Lepidoptera: Arctiidae), includeAmsacta moloneyi, commonly

called the hairy cowpea caterpillar a very polyphagous insect that also attacks

groundnuts. The adult is 12-16 mm long with a wingspan of 35-40 mm. The

larva is a hairy defoliating caterpillar with a yellow head and yellowish brown-patterned segments with ochre nipples. Adults appear 3-5 days after the first

substantial rains and lay their eggs on young plants. This species can go through

3 to 4 generations per year. It can be controlled by cultural practices (end of

cycle ploughing, late sowing). Treatment of young larva with insecticides such

as endosulfan (250 g a.i./ha), monochrotophos (300 g a.i./ha) or fenvalerate

(100 g a.i./ha) and biological control with Bacillus thuringiensis are also

recommended.

Groundnuts are attacked by various species of hairy caterpillars in other countries.These all belong to the family Arctiidae and includeAmsacta albistra ,Amsacta

moori andDiacrisia obliqua.

2.11 Harvesting/Digging

Optimal harvesting date is one of the first problem to be solved. Flowering is

indeterminate in the groundnut; there is therefore a variable proportion of mature,

immature and developing pods at the end of the crop cycle. Premature harvesting

of the crop leads to quantitative losses in production, impacts on oil and proteincontent and on seed viability. If the soil is moist, keeping non-dormant varieties

in the field for longer than the average cycle duration causes high level of

germination of mature seeds while still in the pods. This delay exposes pods to

pest attack; increases seed acidity and aflatoxin contamination, which have direct

consequences on depreciation of seed quality. The most pertinent test for

monitoring groundnut maturity is checking the internal parenchyma of the pods.

It must be turgid, smooth, and dry ranging from white to dark brown. Mature

pods are adequately indicated by the presence of several brown spots. Fields

must be sampled from the theoretical date of pod maturity (varietal cycle) by

pooling several plants and analyzing their pod maturity. The crop can be harvested

once there are 70-80% of mature pods. In non-dormant varieties, the crop is

considered to be mature when 2% of the plants have germinated seeds.

Digging consists of cutting the main root below the pod bearing area. Plants are

then dug up and shaken in order to remove soil adhering to the pods. This

operation is generally manual. The main root is cut with a sharp tool, plants are

then manually dug up, shaken and placed into stacks for rapid curing. Theseoperations take an average of 150 hours per hectare but can very easily be


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mechanized. A simple tool, drawn by an animal can be used. It consists of a

triangular blade 20-50 cm wide (depending on the type of cultivation) supported

by a metallic framework with two steering arms, a front wheel and a hook for

the harness. With this equipment, digging is three times faster than by hand.This basic equipment can also be used as a weeding hoe.


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Post-harvest technology

1. Introduction

Seed quality mainly depends on following appropriate handling and storage

techniques for the harvested crop. Handling facilitates the selection of the best

seeds while storage conditions ensure the conservation of high seed quality.

Groundnut seeds are protected by a shell which acts as an excellent natural

barrier protecting the seed from deteriorating agents. However, this shell should

be perfectly intact in order to protect the seed. Removal of damaged pods is

therefore necessary. Crop residues mixed with the pods are often sources of

contamination (insect eggs, larvae and adults, fungal spores, etc.). They also

represent a pointless use of storage capacity and should be removed.

Phytosanitary protection is equally critical to conservation of the overall value

of the seeds.

Seed quality depends on the following compulsory steps:

good quality stored products;

following recommendations for phytosanitary protection and periodic

inspection especially during warehousing;

appropriate fitting of storage facilities.

2. Handling of the harvested crop

Groundnuts lose their seed value at maturity if they are not correctly handled.

Setting up a stock of quality seeds begins with harvest at optimal pod maturity,

good digging conditions (loose soil, appropriate equipment, rapid harvest) and

adequate curing.

2.1 Curing

Pods with 30-40% water content cannot be stored immediately after harvesting

without them overheating. Likewise, handling of newly harvest pods with seeds

still adhering to the hull could provoke irreversible biological damage and partially

alter the seeds ability to germinate. Curing rapidly reduces pod water content

to about 15%, then gradually to 8-10%. The use of high temperatures or brutal

drying is not recommended.

Pods can either be naturally or artificially cured. In arid savannah areas, uprootedgroundnut plants are inverted, arranged in small heaps and left to dry for one or


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two days. These are then assembled into large stacks with the pods placed towards

the inside, preferably forming a central aeration chimney. In humid areas, the

uprooted plants are dried for several days on wooden racks (stack poles) or on

raised platforms before stripping. Pods are then cured in thin layers, small bagsor baskets.

Under mechanized farming systems, combine harvesters collect windrows, strip

and clean pods in one single operation. The pods are then artificially cured in

drying trailers. Air flow temperature should be 5-6C above ambient tempera-

ture but should not exceed 35C. Optimal depth varies from 0.6 to 3 meters

according to pod water content and the type of curing equipment used.

2.2 Stripping/Winnowing

Pods are stripped at about 2 to 6 weeks after harvesting, when the pod water

content stabilizes at around 10%. This operation consists of separating the pods

from the vegetative parts of the plants (vines). In traditional farming systems,

manual stripping is the rule. Pods are individually detached from the vines and

therefore dry very quickly stabilizing at 6-8% moisture content. The process

results in a perfect quality product. Pods are separated from the vines but are

kept intact. This technique is used for the production of edible or confectionery

groundnuts in order to minimize pod damage and contamination byAspergillusflavus. However, stripping is most often done using sticks or flails. These reduce

the heap of groundnut plants to mixture of chopped vines and partially broken

pods that are then separated by winnowing.

Several types of mechanical combines can be used to strip groundnut windrows

with less than 10% moisture content. The operation of these combines is based

on the following principle. Groundnut plants are manually fed, pod first, into

the combine. Stripping is achieved by friction between the stripper bars against

the base of the plant and the pegs. The stripped product is evacuated across a

counter stripper made up of a cylindrical grid. Large pods retained by the grid

are carried along by the rotation of the combine. Pods are then stripped a second

time. A built-in blower separates the trash from the finished product. The intake

speed, selection of the grid, combine rotation speed and airflow speed must be

regulated (by adjusting the opening of the air intake shutters).

Under mechanized farming systems, modern digging and combining equipment

(high capacity machines) considerably reduce the operation time. This can leadthe producer to strip an insufficiently dried product. Although this is not important


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in confectionery or edible groundnuts, it can damage seeds by causing

microscopic lesions that alter their ability to germinate.

3. Seed processing

3.1 Sieving

This operation is generally done on the farm or at the collecting point. The

classic sieve consists of a hexagonal or cylindrical cage made from bars. It allows

part of the trash including sand, straw and broken pods to be eliminated. However,

it cannot eliminate pods of other varieties, empty pods (pops), partially filled or

immature pods. This is the most basic cleaning operation.

3.2 Density separator

Groundnuts that have been stripped and winnowed using traditional methods

are still highly contaminated by trash. A density separator can be used to get

good quality seeds with a high level of varietal purity, good maturity and absence

of foreign bodies and empty pods (pops). This process allows improvement of

seed quality during drought years and it consists of two elements:

a shaker, equipped with sieves adapted to the treated variety that eliminate

trash (sand, straw, stems) and undersized pods;a blower with adjustable airflow that runs along a sloping surface. Pods are

separated, while falling through the air stream, according to density. Pops

and partially filled pods are ejected outside whereas full pods fall into a

collecting bin.

The shaker and the blower are motorized (electric or gas engine). Gas engines

must be equipped with an oil bath filter since the machine operates under rather

dusty conditions. Adjustments can be made using a yield valve on the feeding

tray. Adjusting the slope of the shaker sieves, the airflow valves or the lowerplate of the sloping surface permits regulation of the reception opening for

good pods (the smaller the opening, the greater the segregation based on pod

weight).

Density separation considerably improves the quality of seeds in hulls, especially

after a year of drought. For Virginia type groundnuts, seed yield is increased by

an average of 9%. This translates into a mean decrease of 10 kg of seeds in shell

per hectare.


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3.3 Packaging

Pods can easily be stored in bulk following the recommendations outlined in

paragraph 4.2. Storage in clean jute or woven polyethylene fiber bags ensuresthe best protection of groundnuts and facilitates manipulation of stocks (manual

or palletized). Groundnut seeds must only be stored in bags or drums according

to recommendations presented in the following chapter. Each bag must be

properly labeled. Labels must show batch origin, year, level of multiplication,

seed weight and eventual phytosanitary treatments.

4. Seed storage and conservation

Groundnut can either be shelled or stored in hulls (improved seeds, communalstocks, buffer stocks of shelling plants).

Seeds in hulls are less exposed to different deteriorating agents and can be

conserved quite well for short periods. When stored in heaps, pods must be

treated with layers of insecticide followed by a final overall treatment. This

requires extensive waterproof storage areas or high capacity warehouses (600-

800 tons). Handling costs are proportionally high and could be minimized by

only storing properly cleaned, good quality batches.

Shelled groundnuts are fragile and are exposed to various agents that cause

physical, chemical and biological deterioration. They rapidly lose their seed value

when stored under natural conditions, especially in tropical areas. The height of

stacked bags should be limited to avoid crushing the seeds. Shelling methods

strongly influence seed quality (see chapter on industrial seed processing).

4.1 On-farm storage of pods

Farmers only keep limited quantities of groundnuts because of financial and

logistical reasons. They rarely distinguish between seed groundnuts and those

destined for sale (or their own consumption). Protective insecticides are rarely

used since farmers consume some of the groundnuts themselves. In humid tropical

areas with two rainy seasons, farmers store their seeds in a ventilated area where

they fumigate them. This storage method is absolutely inappropriate and generally

leads to considerable losses caused by insects and fungi (more than 30%). Farmers

can equally use communal facilities for storing large quantities. However, co-

management is often problematic for three reasons: contamination of the entirestock by poor quality batches, lack of confidentiality and restrictions to seed


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withdrawals to satisfy the farmers financial needs. Groundnut storage is often

conducted by salespeople who are not concerned about quality in general and

even less so by the specific requirements needed for conserving seed quality.

4.2 Collective or industrial storage

Pods must be stored according to well-defined technical recommendations in

order to provide a quality product and to ensure profitability.

Groundnuts should be stored as follows:

collect quality raw material (well filled mature pods), clean, free from visible

insect damage, well cured (6-8% water content);

clean storage facilities;treat storage facilities and seeds (paragraph 5);

check seeds regularly during storage (every 15 days or once a month

according to storage period).

4.3 Storage of shelled groundnuts

This system is rarely used on farms since shelled groundnuts are more fragile

and require expensive, hermetically sealed packaging (plastic or metallic drums).

After shelling, specific procedures must be followed in order to ensure seed

quality. Two processes are recommended: refrigerated storage and controlled

or modified atmosphere storage.

4.3.1 Refrigerated storage

This system is simple, tried and tested and results in excellent long-term storage

(over three years). However there are certain technical and financial constraints:

the stock is physically blocked in the store during the entire storage period;seeds must all be unpacked at one time and certain precautions must be

taken. For example, the temperature must be increased gradually, especiallyduring the rainy season and seeds must be rapidly used (within a few weeks)before they lose their viability;the cost increases sharply with storage time because energy consumption is

high.

4.3.2 Storage under controlled or modified atmosphere

Seeds are placed and maintained in anoxic conditions in either a complete vacuum

or in a modified atmosphere (vacuum replaced with Nitrogen or Carbon dioxidegas).


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Seeds can be maintained under these conditions for medium term periods (18-

24 months) by using extruded multi-layered packets that have a high mechanical

resistance and are impermeable to gases. A package thickness of 60m is adequate

for small quantities of up to 1 kg (e.g. storage of collection samples) however athickness of 90m is recommended for larger quantities (1-10 kg). This isespecially recommended for vacuum packaging where stretching is an importantconsideration. Controlled atmosphere storage is not only cheaper thanrefrigerated storage but there are also no chemical residues on the seeds (seeds

can be untreated). Seeds are therefore not hazardous and can be used without

special protection or authorization. Resistance or tolerance to pesticides can

also be avoided.

Anoxia eradicates insect pests especially the groundnut seed beetle. Trials wereconducted in Senegal on seeds that were artificially infested with C. serratus

and packaged under vacuum for 1-42 days (complete vacuum at 0.26 atm,

compensated vacuum (0.79 atm) with technical Nitrogen (98% N2) or with

additional CO2). In all cases, beetles were completely eradicated in less than 21

days.

Seeds packaged with Nitrogen, either with or without addition of CO2

under a

slight vacuum are completely viable after 18 months of storage at ambient

temperature. Seeds must be stored in a well-ventilated area and protected fromrodents that could damage the bags. Leakage of air into the packets is the maintechnical problem. In order to avoid this, the sealing machine must be properlyadjusted (welding quality), the bags must be of good quality and particular caremust be taken during handling. The seed value of the product depends on itsinitial quality and careful compliance with specifically adapted curing and shelling

techniques.

4.4 Some technical aspects of the industrial preparation of ready-to-use

groundnut seeds

An experiment was conducted in Senegal on the use of ready-to-use coated

groundnut seeds to improve financial and technical management at all stages of

the supply chain. All the difficulties associated with managing seeds in hulls are

avoided using this process:

minimize the volume to be stored;avoid losses and cheating caused by contaminants (sand, soil, other waste,etc.);

eliminate bad farmer practices (partial self-consumption of seeds, absenceof insecticide treatment, incorrect fungicide application).


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Although coating technology offers many advantages, it requires careful

inspection of industrial handling, packaging and storage of the final product.

4.4.1 Mechanical shellingThis first step of the manufacturing process is critical to product quality.

Mechanical shelling is relatively brutal and can cause severe damage to the

seeds (splitting, cracking). Operator expertise is fundamental to reducing the

risks of visible and invisible lesions.

Operating principle

A mechanical sheller is equipped with a head made from perforated or barred

semi-cylindrical grills, which form a cage. Hulls are spread and broken by arotor inside the cage. A pre-sorting is done by a cleaning system (sieving

and blowing), designed to eliminate or collect by-products, broken or

immature groundnuts.

A grading shaker that allows unshelled groundnuts to be separated from

whole and broken groundnuts completes the operation.

Influence of batch quality on shelling

The level of broken kernels increases when immature pods are harvested,

when groundnuts have been beaten with a stick, mechanically (+10%), ortoo late (+5% per month). This also occurs when pod moisture content is

less than 5-6% (in the Sahel it can fall below 3%).

Importance of optimizing adjustments

For a batch of a given quality, the yield of whole kernels is significantly

decreased if the grills hole size is smaller than the groundnuts, if the rotor

speed is excessive and the feeding rate of the machine is too high (a feeding

regulator may be required).

These requirements slow shelling speed and allow a judicious choice to be made

between yield and quality. Since the pod size for each batch may be relatively

heterogeneous, pre-calibration of the groundnuts is recommended in order to

optimize the yield of whole seeds.

Electronic color sorting

Color sorters use color-based systems pre-set by the user. This principle

gives an excellent reproducibility of the results, with a high yield for bothvisible and invisible wavelengths.


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The sorter consists of the following equipment:

a vibrating electromagnetic hopper for precise feeding of the system;

a steeply inclined descending chute aligning, directing and accelerating the

seeds;an examination field composed of fluorescent lights, electronic optics

opposite to reference screens;

complex computerized equipment for data collection and analysis;

an ejector that uses short blasts of compressed air to blow the offending

kernel (darker or lighter than the variety standard) out of the stream of

groundnuts.

Wavelengths reflected by each object arriving in the examination field are captured

by the optical systems and transmitted to photoreceptors that transform theminto electric signals. These are then analyzed by the computerized equipment.

When a defective groundnut is detected it is eliminated by a blast of compressed

air.

The use of clean standard sized groundnuts (for adjusting sorting rate and ejection

speed) as well as a suitable environment (stable power supply, availability of

filtered and cooled compressed air and a clean area with air conditioning) are

critical for successful color sorting.

4.4.2 Seed coating

The typical coating system consists of:

a feeding tray regulating the flow of seeds to treat;

a treatment feeder to deliver the appropriate rate of chemical;

a performing system that compiles the flow of seeds and chemical in order

to ensure proper treatment rate (mechanic or electronic control);

a mixing drum to homogenize the distribution of the treatment to all theseeds (this is equivalent to a draining or pre-drying system);

a conveyor belt to transfer the seeds to the weighing-packaging area.

The principles for an optimized use of the system are:

excellent quality seeds (seed value and integrity);regular seed feeding rate;precise chemical feeding (fungicide or fungicide + insecticide);reliable and rapid control system for seed feeding;

chemical treatment adapted to the process (stable active ingredients, slowdecanting, good coating ability) and to the local soil micro flora.


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5. Phytosanitary protection of stored seeds

Control of storage pests is of critical importance. This is even more so in tropical

countries since agricultural production does not always meet demand. Local

environmental conditions are also favorable to pest development.

Groundnuts characteristically form their pods in the soil and are therefore

vulnerable to attack by pests such as termites (Isoptera) and millipedes (Myrapoda

and Diplopoda). These can cause yield losses and reduce the quality of the

harvested crop by damaging hulls. These lesions become gateways for fungal

infection, notably Aspergillus flavus, the species responsible for aflatoxin

contamination.

Severe attack by seed bugs (Aphanussordidus, Heteroptera: Lygaeidae) are

sometimes observed on drying pods in the fields. The nymphs and adults feed

by making fine perforations in the hulls. This causes very little visible damage

but causes seed desiccation and greatly reduces seed viability.

Rodents also cause field losses to the drying crop. They are of variable diversity

and importance, however, there are two main species: one diurnal species, the

stripped ground squirrel (Xeriuserythropus) and one nocturnal (Cricetemys

gambianus).

The principle stored product pests, the seed bug (Heteroptera: Lygaeidae) and

the groundnut seed beetle (Caryedoncerratus) can cause significant damage.

Other insects, particularly Khapra beetles (Trogodermagranarium E.), as well

as flour beetles, Triboliumcastaneum H. and T. confusum are also important,

especially on shelled groundnuts.

The groundnut seed beetle is the most formidable long-term storage pest (Gillier

& Brockele-Morovan, 1979). The larva develops inside the pods and is therefore

protected from insecticidal dusts and sprays.

However, local farmers tolerate damage caused by this pest, as long as losses

are not spectacular. The detection of seed beetle damage and hence the decision

to apply treatment is sometime too late. The possibility of future attack is

unrecognized by farmers since they are unaware of the multivoltine life history

of certain pests. Farmers tolerate a certain level of damage since they accept the

idea that the pests take their share of the harvest! Such fatalism is an exampleof the ambiguous relationship that farmers have with their environment.


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5.1 Insect control

5.1.1 Contact treatments

Future stacking sites must be treated with insecticide dust before windrows andstacks are formed for drying the groundnuts. A peripheral band should also be

treated to protect the site. Groundnuts are thus protected against termites and

seed bugs. Storage areas, containers, drums, bags and storage equipment

(conveyors, etc.) must be treated before storing groundnuts. Cleaning these

areas can be followed by fumigation or spraying with insecticides. Pesticides

are applied using a sandwich technique. Seeds are dusted during bagging, and

then an insecticidal dust is applied between each layer of bags.

Organophosphates are contact insecticides currently used. Bromophos (500 g

of 2% dust/ton) or idofenphos (1000 g of 2% dust/ton) are most commonly

used products. Other available products with long residual activity include:

- organophosphates: ethyl-pyrimiphos (Actellic), methyl-chlorpyriphos

(Reldan). Their residual activity is low in open air but exceeds 6 months

on stored seeds protected from light;

- syntheticpyrethroids: Deltamethrine (K. Othrine).

Contact insecticides ensure good protection against insects once groundnutsare not previously infested. For this reason, preventive fumigation of seed

groundnuts must be carried out.

5.1.2 Fumigation

Groundnut seeds (sorted pods or kernels) can be treated under airtight plastic

tarpaulins, hermetically sealed silos or warehouses in a fumigant-saturated

atmosphere. Groundnuts are currently fumigated in pyramidal heaps under plastic

tarpaulins. Bags are arranged to form a pyramid that is slightly smaller than thetarpaulin. The base is sealed with a row of sandbags.

Methyl bromide (CH3Br), long used for fumigation, is now prohibited by

international legislation since it contributes to the greenhouse effect. This product,

used in gaseous form, has an instantaneous impact on pest, eradicating all

developmental stages (eggs, larva, and adults). Hydrogen phosphide (PH3), the

only remaining authorized fumigant, is available in tablet form. Its release is

much slower than methyl bromide and its use requires absolute adherence to

manufactures recommendations in order for it to be equally effective. For this


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reason, under the arid conditions in the Sahel, a humid environment must be

created under the fumigation tarpaulin. Small, water-filled cups or dampened

bags are placed on the surface of the heap of groundnuts being treated. This

ensures a rapid gas release that guarantees immediate eradication of the pest.

The gas is produced from the breakdown of aluminum phosphide tablets

(Phostoxin). Hydrogen phosphide, also known as phosphine gas, is obtained

when its precursors (aluminum or magnesium phosphide) are exposed to humid

conditions. Tablets must be placed on small saucers in order to recuperate

powdery residues that still contain traces of aluminum phosphide. Successful

fumigation depends on several factors. The most important are: ambient moisture,

fumigant dose and fumigation duration. Fumigant dose can be reduced in airtight

treatment areas with high temperature.

Groundnuts have relatively high absorption rates for hydrogen phosphide: 50%

and 80% respectively for shelled and unshelled groundnuts with a 5-day

fumigation at 25C3. In practice, a 3-4 days treatment with a dose of 2 g/m3 and

3 g/m3 PH3can be used respectively for shelled and unshelled groundnuts stored

under tarpaulin or in fairly airtight warehouse (considering a 50% loss coefficient).

Stored groundnuts must be regularly checked for sanitary problems, and a seed

sample should be analyzed on a 3-week basis to ensure good conservation and

eventually implement corrective measures.

5.1.3 Physical and mechanical methods

These low technology methods are cheap, effective and readily available to

farmers. Several techniques are used, depending on the area.

Groundnuts are mixed with powdered minerals (ashes, sand, etc.) that act

as abrasives or physical barriers.

Hermetically sealed containers in which anoxic conditions limit insect

development.

Temperatures are bellow (40-45C) the optimum for

insect development.

3 Laboratoire Denres Stockes, 33150 Cenon - France


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Solarisation of groundnuts under plastic or polyethylene mulching

(thermosolar treatments) which greatly affect bruchids. Precautions must

be taken to avoid deterioration of the germinative capacity of the seeds.

6. Seed physiology

Planting non-viable seeds that cannot germinate and therefore ensure a good

harvest, is the farmers greatest risk. Determining seed crop value is the ultimate

objective of any analysis. However, parameters that determine seed quality may

be prioritized differently, depending on the user. There are recommendedanalytical methods based on standardized international seed trading guidelines.

These have been ratified within the framework of the International Seed Testing

Association (ISTA).

6.1 Germination

Germination is defined as the appearance and development of the embryo, to

form the essential organs of the seedling. The seeds ability to produce a normal

seedling under favorable conditions can be determined by examining these organs.

The mature groundnut seed is made up of an embryo comprised of two

cotyledons, a short hypocotyl, the plumule and the primary root. The plumule isformed by a central axis and the two cotyledon axes. It already contains nineembryonic leaves. These essential organs originate from tissue differentiation

during the embryos development inside the seed.

Viable seeds begin germinating when placed in a favorable environment

(temperature, moisture, and oxygen). Germination takes place in several stages:

imbibition;activation of enzymes;

growth of the embryo;rupture of the testa;elongation and emergence of the radical;

growth of the terminal bud and embryonic axis.

Imbibition is based on the seeds chemical composition, water availability in its

environment and the permeability of the testa. Protein-rich seeds need to imbibe

2-5 times their dry weight in water to initiate germination. This is relatively high

when compared to certain sugar rich cereal species. These need to absorb only

one and a half to twice their dry weight in water. In order to germinate, legumes


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and cotton need a minimum water content of 50-55% whereas cereals need

30-35% which is close to the observed water content at physiological maturity.

Water activates the enzymes responsible for hydrolysis of nutritional reserves(lipids, sugars and proteins). It is essential for transport and utilization of the

simplest and most mobile components (glucose, amino acids, etc.) by the growing

embryonic axis. Enzymes catalyze the reaction needed for the synthesis of new

material required for tissue differentiation and growth of the embryo.

Germination in peanuts is epigeal. The cotyledons and the sprout are carried

above the soil by the elongating hypocotyl. Seed viability can be determined by

germination test. Four repetitions of 100 seeds or eight repetitions of 50 seeds

(a total of 400 seeds are used). Seeds are equally spaced on a moist substratethen placed in an incubator at 30C and 90% RH. Seeds are evaluated after five

days (germinative vigor) or 10 days (germinative ability). They are also classified

as normal seedlings, abnormal seedlings and ungerminated seeds.

6.2 Dormancy and methods for breaking dormancy

Dormancy is a natural phenomenon in the plant kingdom. It is defined as the

inability of newly harvested seeds to continue their development under favorable

environmental conditions (temperature and humidity). Generally, dormancy isan absence or a significant reduction in seed viability, even under favorable

conditions. Dormancy is an adaptation that allows plant to survive particular

climatic conditions. Seed germination is spread over time since the intensity of

dormancy varies within a seed population.

Natural factors or climatic changes can break dormancy. It is absent in Spanish

and Valencia type groundnut or is naturally broken several weeks after seed

maturity. It can cause pre-harvest germination in the field when harvesting is

delayed and the soil is still moist (irrigation, end of season rains) and even during

storage in unseasonably wet periods. This type of unwanted germination

considerably reduces seed yield and quality; such seeds are usually downgraded

and used for oil production. Virginia type groundnuts have a longer dormancy

of four months or more.

Endogenous metabolic inhibitors cause dormancy in groundnuts. These are

generally enzymes that block hydrolysis of nutrient reserves and nutrient transport

to the embryo. The synthesis of new material is thereby inhibited.


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Previous work has shown that product such as ethylene (3.5ppm induces excellent

germination). Ethephon can also be used to break dormancy in groundnuts.

Ethephon or ethrel, originally a growth regulator, progressively decomposes

into mainly ethylene as well as several other substances. It is available in liquidor powder form. The powder is added to the fungicide-insecticide mixture and

the liquid is sprayed onto untreated seeds. Heat treatments can also break

dormancy (40-45C for 15 days) but this long, slow treatment is not very

convenient.

Groundnut Seed Project GSP

Contact address / Principal addresses

Project Executing Agency (PEA), Farid WaliyarICRISAT, Patancheru, 502 324, Andra Pradesh, India

Bonny Ntare, Project Manager

ICRISAT-Bamako, B.P. 320, Bamako, Mali

08 eng seed prod guide april1

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